Suits of ancient power armor are remnants from an age of lost technological marvels. Most suits will be found in varying levels of disrepair, and are sometimes mistaken for statues.
Power armor operators have AC as plate. The suit of armor has a pool of hit points which is depleted prior to the user taking any damage. Each suit of ancient power armor has a level, which corresponds to the number of hit dice rolled for max armor HP. For example, a 6th level suit of armor will have 6d8 HP. To randomly determine armor level, roll 2d4.
Movement while wearing power armor is 90′ (3/4 unencumbered human movement) but is not decreased further by any but the most extreme encumbrance. Depending on the suit in question, using conventional weapons may be awkward (resulting in an attack roll penalty).
There is a 50% chance that power armor will have offensive systems, which by default are a pair of energy canons (one mounted on each arm). Each blast consumes a charge from a super science battery, and does 1d8 damage per blast. Both arm canons may be fired in a single round.
Operating the power armor requires a successful “use super science” check. This is 1 in 6 for most classes, 2 in 6 for dwarves/engineers (*); the chance is also raised by 1 for high intelligence (13 or greater). No more than one check per character is allowed per suit. One check is required for mobility and defensive systems, another check is required for offensive systems, if they exist. A week of work, plus another successful super science check, will repair 1d8 HP worth of damage. Referee ruling may require special materials or GP expenditure as well.
When the power armor HP is reduced to 0, it ceases to function immediately, damaged beyond repair. Any extra HP damage spills over onto the user. Extraction from the suit requires 1d4 rounds and a successful strength check, or a full turn of careful manipulation.
In no circumstances can a wearer of power armor ever cast spells or use magic items.
Many varieties of ancient power armor exist. For example, some are designed to function underwater and supply oxygen. Others have variant offensive systems, such as flame throwers. Some suits of power armor also grant immunity to certain forms of attack, such as fire or electricity.
(*) I haven’t posted in detail about it yet, but the engineer is a human reskin of the dwarf B/X class.